Brassica rapa is a plant species that has been widely cultivated into many forms, including the turnip (a root vegetable), komatsuna, napa cabbage, bomdong, bok choy, and rapini.
Brassica rapa subsp. oleifera is an oilseed commonly known as turnip rape, field mustard, bird's rape, and keblock.[1] [2] [3] [4] [5] Rapeseed oil is a general term for oil from some Brassica species. Food grade oil made from the seed of low-erucic acid Canadian-developed strains is also called canola oil, while non-food oil is called colza oil. Canola oil can be sourced from Brassica rapa and Brassica napus, which are commonly grown in Canada, and Brassica juncea, which is less common.[6]
The geographic and genetic origins of B. rapa have been difficult to identify due to its long history of human cultivation. It is found in most parts of the world, and has returned to the wild many times as a feral plant or weed.
Genetic sequencing and environmental modelling have indicated that ancestral B. rapa likely originated 4000 to 6000 years ago in the Hindu Kush area of Central Asia, and had three sets of chromosomes, providing the genetic potential for a diversity of form, flavour, and growth. Domestication has produced modern vegetables and oil-seed crops, all with two sets of chromosomes.[7] [8]
Oilseed subspecies (subsp. oleifera) of Brassica rapa may have been domesticated several times from the Mediterranean to India, starting as early as 2000 BC.[9] There are descriptions of B. rapa vegetables in Indian and Chinese documents from around 1000 BC.
Edible turnips were possibly first cultivated in northern Europe, and were an important food in ancient Rome. The turnip then spread east to China, and reached Japan by 700 AD.
In the 18th century, the turnip and the oilseed-producing variants were thought to be different species by Carl Linnaeus, who named them B. rapa and B. campestris. Twentieth-century taxonomists found that the plants were cross fertile and thus belonged to the same species. Since the turnip had been named first by Linnaeus, the name Brassica rapa was adopted.[10]
Many butterflies, including the small white, feed from and pollinate the B. rapa flowers.
The young leaves are a common leaf vegetable and can be eaten raw; older leaves are typically cooked. The taproot and seeds can also be eaten raw, although the seeds contain an oil that can cause irritation for some people.[11]
| Cultivar | Image | Name |
|---|---|---|
| Bok choy | Brassica rapa subsp. chinensis | |
| Bomdong | Brassica rapa var. glabra | |
| Choy sum | Brassica rapa subsp. parachinensis | |
| Field mustard | Brassica rapa subsp. oleifera | |
| Komatsuna | Brassica rapa subsp. perviridis | |
| Mizuna | Brassica rapa var. nipposinica | |
| Napa cabbage | Brassica rapa subsp. pekinensis | |
| Rapini | Brassica rapa var. ruvo | |
| Tatsoi | Brassica rapa subsp. narinosa | |
| Turnip | Brassica rapa subsp. rapa | |
| Yellow sarson | Brassica rapa subsp. trilocularis | |